The voltage of the battery!
Did you leave it connected to the AC Adapter for a couple of hours? Li-Ion batteries can react violently when battery voltage drops to low and a charge current is applied to the battery. If this happens then safety circuitry does not allow the battery to be charged and the battery must be replaced. If the battery measures greater than 3V then let it sit connected to the AC Adapter for a couple hours and then try to turn it on. If the measured voltage is less than 2.7V then you likely need a new battery.
Thank you. I ended up ordering a new battery. Took it to Verizon and that's what they suggested after making sure the port was good and tried a new cable.